The sounds of the sea are associated with tranquillity and relaxation. People go to the beach to enjoy the soothing crash of ocean waves. But beneath the surface of the ocean, there is no peace and quiet for whales and dolphins.

The increasing use of the sea for human activities has resulted in a dramatic rise in noise levels. A new film, Sonic Sea, screening at the Environmental Film Festival Australia, shows that the ocean is not at all silent. It highlights our emerging understanding of the consequences of human-produced noise pollution in the ocean.

The documentary, directed by Michelle Dougherty and Daniel Hinerfeld, brings together beautiful cinematography and audio effects that draw viewers into this ethereal underwater world.

When mammals returned to the sea, they evolved to use sound as their primary way to navigate through their environment. This is because sound travels further and more efficiently through water than air.

For marine mammals, using sound to communicate, and to see (echolocate), is invaluable. But this dependence by marine mammals on underwater sound is now a trap; they have nowhere to escape the increasing underwater noise.

Where does the noise come from?

The film presents three major sources of human-produced noise in the ocean: shipping, seismic exploration, and military sonar.

Shipping noise is acoustically overwhelming the ocean, doubling every decade with no hint of slowing. Not only is the number of ships increasing, but they are also getting bigger and carrying more containers.

This noise reduces the distance over which animals can communicate with one another, forcing them to compete with increasing background noise.

Finding mates would become more difficult meaning whales may miss out on the opportunity to breed.

Mass stranding events of beaked whales have been linked to the use of military sonar. It appears that these whales have a marked behavioural response to some types of sonar. This may be why the whales strand at times when military sonar has been used. This has raised serious concerns for the navy about whether, and where, this type of sonar can be used.

Even though seismic explosions, used by oil and gas companies, do not cause direct harm to whales, the blasts do drive them away from the area. Fish, on the other hand, are deafened by these detonations and we have seen a long-term drop in numbers with the prolonged use of seismic air guns.

Turning down the volume

The film presents various solutions to help reduce the amount of noise that is generated and the impact caused to these vulnerable animals.

Our heavy reliance on ships for the transport of goods means we cannot simply stop their movement. But it is possible to implement quieter and more efficient engines and propellers to reduce noise.

When whales are present, harmful activities such as seismic blasts and sonar need to stop.

The film concludes by leaving viewers with the question: what would the world look like if we don’t reduce our impacts? It raises the question of sustainability and the legacy we will leave for future generations once we are gone.

Sonic Sea is screening at the Environmental Film Festival Australia in Sydney on Saturday October 22, 2016.